This invention provides system and apparatus for preventing theft of an aircraft. The system includes both access code input apparatus and starter motor interlock apparatus that prohibits an engine of the aircraft from starting unless the proper code has been supplied.
Theft prevention systems that prevent starting or operation of a vehicle are well known in the art and include the Catalog Number 12XX8415Y sold by J. C. Whitney and Company, 1917 Archer Avenue, Chicago, Ill. 60680. The 12XX8415Y system automatically disables an automobile's starter motor or ignition system whenever the ignition is turned off, and requires the driver to use a keyboard to enter a four digit secret code before re-starting the car. If a thief cuts the wire between the keyboard unit and the portion of the system located at the starter motor, the vehicle remains in a disabled state.
Other teachings of theft deterrent systems and apparatus that use a secret code or personal identification number ("PIN") are provided in several U.S. patents, including:
U.S. Pat. No. 5,111,185--Wherein Kozaki teaches a multi-password anti-theft system for preventing the theft of individual items of a multi-component automobile entertainment system.
U.S. Pat. No. 4,495,114--Wherein Kaish teaches a password-based system for automatically disabling microprocessor controlled electronic equipment when a key event occurs (e.g. when a radio is removed from an automobile). In Kaish's system the user has the option of changing the password.
Applying any of the prior art systems that have been developed for automobiles to an aircraft poses a serious safety consideration that does not occur in land vehicles. Any aircraft system or apparatus that can disable the operation of a starter motor, or that can shut down an engine, must be designed so as to minimize or eliminate the risk that the system could inadvertently disable the aircraft while it is flying. Jones et al, in U.S. Pat. No. 4,891,971, provide a system and apparatus that automatically prevents abnormal start-up of an aircraft turbine engine. Jones et al's system uses inputs from either an airspeed sensor or from a "squat switch" that is connected to the aircraft's landing gear to indicate that the airplane is on the ground before aborting an abnormal start-up. The disclosure of Jones et al is herein incorporated by reference.
Retrofitting an anti-theft system to an existing aircraft has additional complications that are not encountered in similar systems used on land vehicles. One source of complexity and additional cost of installation is posed by the difficulty of routing the necessary electric wiring from the cockpit or passenger compartment portion of an aircraft to the engine compartment or nacelle. This can be particularly difficult in multi-engine fixed-wing aircraft, in which the wiring is run through the wing. Another source of complexity is posed by the requirement, in modern aircraft that have a pressurized cabin, of ensuring that any new penetration of a bulkhead (e.g. running a wire from the instrument panel to an engine) does not introduce an air leak that could affect the cabin pressurization system.
Prior art approaches to using pre-existing wiring to send data and commands are well known. Teaching of this is found, inter alia, in Smith and Laxton in U.S. Pat. No. 4,567,511.